Liquid crystal display panels have a configuration in which a liquid crystal display element is held between paired glass substrates, for example, and have characteristics such as thin profile, light weight, and low power consumption. Having such characteristics, liquid crystal display panels are indispensable for products used in daily life and business, such as automotive navigation systems, electronic book readers, digital photo frames, industrial equipment, televisions, personal computers, smartphones, and tablet PCs. For these applications, liquid crystal display panels in various modes have been developed which employ electrode arrangements and substrate designs to vary the optical characteristics of liquid crystal layers.
Recent display modes for liquid crystal display panels include vertical alignment (VA) modes which align liquid crystal molecules having negative anisotropy of dielectric constant in the direction perpendicular to the substrate surfaces. Vertical alignment mode liquid crystal display panels are used in the applications described above owing to their wide viewing angle. In particular, the following liquid crystal display panels have been put into practical use: multi-domain vertical alignment (MVA) liquid crystal display panels in which one of the substrates is provided with electrode slits and the other is provided with projections, as alignment control structures, for pixel division (alignment division); and patterned vertical alignment (PVA) mode liquid crystal display panels in which both of the substrates are provided with electrode slits for pixel division (alignment division).
The MVA mode and the PVA mode, however, can still be improved in that their response speed is low. In other words, upon application of high-level voltage to switch the mode from black to white, only liquid crystal molecules near the electrode slits and projections react instantly and liquid crystal molecules away from these alignment control structures are slow to respond.
In order to increase the response speed, it is effective to provide an alignment film to the entire surface of each substrate, perform alignment treatment on the films, and provide a pre-tilt angle to liquid crystal molecules in advance. Also in the VA mode, by slightly tilting liquid crystal molecules in advance from the vertical alignment films, liquid crystal molecules can be easily tilted when voltage is applied to the liquid crystal layer, and thus the response speed can be increased.
Examples of a VA mode liquid crystal display device utilizing vertical alignment films whose alignment treatment directions on the substrates are perpendicular to each other to give a twist structure to liquid crystal molecules include a liquid crystal display device disclosed in Patent Literature 1. The liquid crystal display device includes a vertical alignment liquid crystal layer; a first substrate and a second substrate; a first electrode, which is arranged on the first substrate so as to face the liquid crystal layer; a second electrode, which is arranged on the second substrate so as to face the liquid crystal layer; and at least one alignment film, which is arranged in contact with the liquid crystal layer, wherein either the first substrate or the second substrate includes an opaque member, which includes an opaque portion for shielding an intersection between a boundary area of each of the first, second, third and fourth liquid crystal domains, which is adjacent to another one of the liquid crystal domains, and one of the first, second, third and fourth edge portions from incoming light.
Examples of a VA mode liquid crystal display device having a four-division alignment structure in which a pre-tilt angle is provided to liquid crystal molecules in advance include a liquid crystal display device disclosed in Patent Literature 2. The liquid crystal display device includes two polarizing plates whose polarization axes are perpendicular to each other; and multiple pixels. In the display device, the pixels each include a liquid crystal layer containing a nematic liquid crystal material whose anisotropy of dielectric constant is negative, a first electrode, a second electrode facing the first electrode across the liquid crystal layer, and paired vertical alignment films disposed between the first electrode and the liquid crystal layer and between the second electrode and the liquid crystal layer. The first electrode includes a main portion and multiple branch portions coupled with the main portion. The branch portions include a first group with multiple first branches extending in the first azimuth direction in stripes, a second group with multiple second branches extending in the second azimuth direction in stripes, a third group with multiple third branches extending in the third azimuth direction in stripes, and a fourth group with multiple fourth branches extending in the fourth azimuth direction in stripes. A difference between any two of the first azimuth, second azimuth, third azimuth, and fourth azimuth is approximately equal to an integer multiple of 90°, and the azimuths form an angle of approximately 45° with the polarization axes of the two polarizing plates. When no voltage is applied to the liquid crystal layer, the pre-tilt azimuths of liquid crystal molecules near the paired respective vertical alignment films are defined by the paired vertical alignment films.